Recent technological developments and increased public awareness of the need for routine mammographic screening have resulted in a dramatic increase in the detection of small, often nonpalpable breast lesions. Unfortunately, the pace of development of surgical tools has not kept pace with development of the diagnostic tools and removal of these small lesions remains a difficult, time consuming process that is prone to failure. This proposal addresses continued development of a system to allow surgeons to accurately identify the position of tumor margins during breast conservation surgery and needle-localization breast biopsy procedures. In Phase I, a prototype version of the system was constructed and successfully tested on simulated breast lesions. This testing demonstrated that the system has the potential to increase the accuracy of these procedures and reduce the number of surgeries that fail due to incomplete resections or missed lesions. In Phase II, a handheld version of the system will be developed and tested on a variety of tumor geometries representative of those encountered in clinical practice. PROPOSED COMMERCIAL APPLICATION: The commercial potential of this technology is significant. Creare has formed a commercial partnership intended to bring this technology to market.